1. Field of the Invention
The present invention relates to techniques for etching stratified materials with a laser. The invention concerns, more particularly, a method for forming incisions in a stratified material to affect physical or aesthetic properties of the stratified material. The invention has application, for example, to stratified materials that are utilized to form footwear uppers.
2. Description of Background Art
Conventional articles of athletic footwear generally include two primary elements, an upper and a sole structure. The upper is secured to the sole structure and forms a void on the interior of the footwear for comfortably and securely receiving a foot. The sole structure is positioned between the foot and the ground to attenuate ground reaction forces and absorb energy as the footwear contacts the ground. Accordingly, the upper and sole structure operate in concert to position the foot relative to the ground and to protect the foot.
The upper generally extends over the instep and toe areas of the foot, along the medial and lateral sides of the foot, and around the heel area of the foot. Access to the void on the interior of the footwear is generally provided by an ankle opening. A lacing system is often incorporated into the upper to selectively increase the size of the ankle opening and permit the wearer to modify certain dimensions of the upper, particularly girth, to accommodate feet with varying dimensions. In addition, the upper may include a tongue that extends under the lacing system to enhance the comfort of the footwear, and the upper may include a heel counter to limit movement of the heel.
Various materials may be utilized in manufacturing the upper. The upper of athletic footwear, for example, may be formed from multiple material layers that include an exterior layer, a middle layer, and an interior layer. The materials forming the exterior layer of the upper may be selected based upon the properties of wear-resistance, flexibility, and air-permeability, for example. With regard to the exterior layer, the toe area and the heel area may be formed of leather, synthetic leather, or a rubber material to impart a relatively high degree of wear-resistance. Leather, synthetic leather, and rubber materials may not exhibit the desired degree of flexibility and air-permeability. Accordingly, various other areas of the exterior layer of the upper may be formed from a synthetic textile. The exterior layer of the upper may be formed, therefore, from numerous material elements that each impart different properties to the upper.
A middle layer of the upper may be formed from a lightweight polymer foam material that provides cushioning and protects the foot from objects that may contact the upper. Similarly, an interior layer of the upper may be formed of a moisture-wicking textile that removes perspiration from the area immediately surrounding the foot. In some articles of athletic footwear, the various layers may be joined with an adhesive, and stitching may be utilized to join elements within a single layer or to reinforce specific areas of the upper.
Based upon the above discussion, the conventional upper is formed from multiple layers, and each layer may be formed from multiple material elements. In manufacturing the upper, the specific materials utilized for each layer and element are selected and then cut to a predetermined shape. Considerable effort is then expended in joining the various elements together, particularly the various material elements forming the exterior layer of the upper.